1. Field of the Invention
This invention relates to a tong and, more particularly, to a tong having metal surface engaging pads.
2. Discussion of the Technical Problems and Prior Art
As is known in the glass-edge multiple glazed manufacturing art, a pair of glass sheets having their edges welded together at a glass welding station are transported through an annealing lehr to prevent thermal damage to the welded sheets. Thereafter, the space between the welded sheets is filled with a gas and sealed to provide a glass-edge multiple glazed unit. In the art, it is common practice to vertically support the welded sheets by way of tongs when transporting the welded sheets through the annealing lehr.
In general, the prior art tongs are made of pivotally mounted metal arms having asbestos surface engaging pads. The asbestos pads minimize heat loss from the unit to the metal parts of the tongs and are capable of withstanding temperatures of about 1000.degree. F. (540.degree. C.) of the recently welded glass sheets. Asbestos pads, however, have drawbacks. More particularly, the asbestos pads when exposed to continual temperature cycles, i.e., room temperature at the exit end of the annealing lehr to about 1000.degree. F. (540.degree. C.) at the welding station environment, break down to a powder. Further, as the welded glass sheets are moved between the asbestos pads, the edge of the welded sheets contacts same causing the pads to flake. As is well known, asbestos powder or flakes create a potential health hazard.
In the prior art, for example, in U.S. Pat. Nos. 166,599; 1,428,679; 3,025,638; 3,089,727; 3,363,930; 3,390,911; 3,391,958; 3,392,006; 3,456,985; 3,830,540 and 3,913,966, there are taught tongs having metal; wood; rubber; plastic and/or refractory surface engaging pads. Although these prior art tongs eliminate the drawback of asbestos pads, they are not acceptable for use in transporting welded glass sheets from a welding station through an annealing lehr. As was mentioned, the temperature of recently welded glass sheets is approximately 1000.degree. F. (540.degree. C.); and therefore, surface engaging pads made of wood and rubber are not acceptable because they cannot withstand the high temperatures. The solid metal surface engaging pads are not acceptable because they can create thermal shock, i.e., rapid extraction of heat from the welded sheets through the metal pads. When this occurs, the welded sheets can fracture. The use of refractory pads is not acceptable because they are hard; and at temperatures of 1000.degree. F. (540.degree. C.), the glass is plastic and can be marred by the refractory pads.
It would be advantageous therefore to provide a tong having surface engaging pads that do not have the limitations of the prior art.